Skeletal muscle lymphoma: observations at MR imaging

Diagnostic challenge: Combination of magnetic resonance imaging and serum soluble Interleukin-2 receptor in soft tissue non-hodgkin lymphoma

Purpose

Non-Hodgkin lymphoma (NHL) sometimes occurs in soft tissue (referred to as soft tissue lymphoma or soft tissue NHL), often mimicking soft tissue tumors. Despite some clinical indicators, accurate diagnosis of soft tissue NHL before biopsy remains challenging. We investigated the diagnostic value of serum soluble interleukin-2 receptor (sIL-2R) levels and magnetic resonance imaging (MRI) as an initial tool to assess the likelihood of soft tissue NHL.

Methods

We analyzed 36 cases of pathologically proven soft tissue NHL initially suspected as soft tissue tumors alongside 48 control cases of soft tissue sarcoma or carcinoma. Patient medical charts and MRI scans were retrospectively reviewed and statistically analyzed, focusing on assessing the diagnostic efficacy of soft tissue NHL.

Results

The diagnostic accuracy of soft tissue NHL combining the appearance of homogeneity on MRI (T2-weighted and/or short-time inversion recovery [STIR] images) and sIL-2R value (≧ 904 U/mL) yielded a sensitivity of 78 % and 86 %, and specificity of 83 % and 88 %, respectively. Meeting one or both criteria increased the sensitivity to a maximum of 92 %, albeit with a specificity of 71 %. When both criteria were met, sensitivity and specificity were 72 % and 100 %, respectively.

Conclusion

The integrated approach of combining MRI and sIL-2R demonstrated excellent efficacy in predicting the diagnosis of soft tissue NHL, which was initially referred to as soft tissue tumor.

Orofacial intramuscular lymphoma: first presentation

The term lymphoma includes a wide variety of different clinical entities including diffuse large B-cell lymphomas (DLBCL). Skeletal muscle or intramuscular lymphomas represent less than 2% of B-cell Lymphoma, they are quite rare, even more in the orofacial area. We present the case of a painless growing mass of the right cheek mimicking a chronic oral cellulitis in a 34-year-old man. Magnetic resonance imaging (MRI) of the mandible revealed a well-defined 7x3cm mass around the core of the mandible that invades the buccal floor and the subcutaneous planes. A whole-body 18F-FDG PET/CT for the initial diagnosis revealed an intensely isolated hypermetabolic band corresponding to a voluminous tumoral permeation. The diagnosis of a skeletal muscle diffuse large B-cell lymphoma was established after an intraoral biopsy. It was treated with 4 chemotherapy cures and showed complete remission at one year of follow-up. This atypical form of lymphoma should be integrated into the differential diagnosis of soft tissue tumors in the oral cavity.

Clinical Presentation and MRI Characteristics of Appendicular Soft Tissue Lymphoma: A Systematic Review

Appendicular soft tissue lymphoma (ASTL) is rare and is frequently misinterpreted as soft tissue sarcoma (STS). Studies investigating magnet resonance imaging (MRI) characteristics of ASTL are scarce and showed heterogenous investigation criteria and results. The purpose of this study was to systematically review clinical presentations and MRI characteristics of ASTL as described in the current literature. For that purpose, we performed a systematic literature review in compliance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Patient demographics, clinical presentation and MRI imaging characteristics of ASTL were investigated, resulting in a total of nine included studies reporting a total of 77 patients. Signal intensity of lymphoma compared to muscle tissue was mostly described as isointense (53%) or slightly hyperintense (39%) in T1-weighted images and always as hyperintense in proton-and T2-weighted images. Multicompartmental involvement was reported in 59% of cases and subcutaneous stranding in 74%. Long segmental involvement was present in 80% of investigated cases. Involvement of neurovascular structures was reported in 41% of cases and the presence of traversing vessels in 83% of patients. The presence of these findings should lead to the inclusion of ASTL in the differential diagnosis of soft tissue masses.

Imaging features of skeletal muscle lymphoma: a case report and literature review

BACKGROUND

Diffuse large B cell lymphoma (DLBCL) is the most common type of non-Hodgkin lymphoma (NHL), occurring predominantly in older people. Skeletal muscle lymphoma is a rare form of DLBCL, most frequently affecting the thigh, upper extremities, calf, and pelvis.

CASE PRESENTATION

We report a case of skeletal muscle DLBCL that was diagnosed using ultrasound (US)-guided biopsy. A 70-year-old man presented with progressive swelling and pain in the left lower extremity and an elevated erythrocyte sedimentation rate (ESR) and serum C-reactive protein (CRP), ferritin, and CA125 levels. US, magnetic resonance imaging (MRI), and computed tomography (CT) showed diffuse lesions in several muscles of the left lower extremity. Positron emission tomography/CT (PET/CT) showed FDG-uptake in the affected muscles. The patient was treated with chemotherapy and achieved a good response. A systematic review of the literature published between 1992 and 2019 was conducted to investigate the role of imaging, including imaging-guided biopsy, in the diagnosis of skeletal muscle lymphoma.

CONCLUSIONS

Skeletal muscle lymphoma is rare. US and MRI features include enlargement of muscular structures, with preservation of the architecture of the tissue and surrounding anatomical structures. Definitive diagnosis relies on histological and immunohistological analysis of a sample obtained through imaging-guided biopsy.

MRI Features of Presumed Primary Extranodal Lymphoma of the Bulbospongiosus Muscle Causing Stranguria

Hematopoietic neoplasia is common in dogs, with canine non-Hodgkin lymphomas representing more than 80% of all hematopoietic cancer. However, extranodal infiltration of the skeletal muscle by non-Hodgkin lymphoma is rare in humans and dogs. A 9 yr old neutered male English mastiff presented with a 3 wk history of recurrent stranguria, pelvic limb ataxia, and mild proprioceptive deficits bilaterally, worse in the right pelvic limb. MRI showed an expansile ill-defined lesion within the bulbospongiosus muscle. The lesion had intermediate signal intensity to muscle and fat on T2-weighted imaging and was isointense to unaffected muscle on precontrast T1-weighted imaging. Contrast enhancement was heterogeneous and there was digitate signal alteration within adjacent perilesional fat. Ultrasound examination confirmed a hypoechoic lesion infiltrating the muscle. Cytological examination yielded a diagnosis of high-grade lymphoma. This report provides the first description of MRI findings associated with cytologically confirmed lymphoma of the skeletal muscle in the dog. Although nonspecific, the imaging features strongly correlate with those in the medical literature and lymphoma should be considered a pertinent differential in cases presenting with similar imaging findings.

[Imaging characteristics of malignant and benign lesions of skeletal muscle]

There are many different tumors and tumor-like lesions with variable biological behavior that may affect the skeletal musculature. The aim of this study was to review the different intramuscular lesions and to provide a classification based on their radiological patterns. Intramuscular lesions can present as solid, liquid, semiliquid or fat equivalent manifestations and also as diffuse muscle enlargement and muscle calcification. Additionally, lesions with mixed patterns of the aforementioned alterations can also occur. Benign and malignant muscle lesions can often manifest with identical radiological patterns, which is why a certain differentiation is often difficult. A systematic radiological description and when possible assignment with respect to etiology and dignity depending on the patient history is necessary in order to recommend a subsequent histological confirmation or to avoid unnecessary confirmation.

Incidental findings in the skeletal musculature on computed tomography

OBJECTIVE

The purpose of this study was to analyze intramuscular incidental findings identified on CT in a large patient cohort.

METHODS

In the time period from 2010 to 2015, a total of 44,794 patients with several diagnoses were investigated by CT. Only those patients who underwent body CT including the neck, thorax, abdomen and pelvic regions after the i.v. application of a contrast medium were involved in the study. There were 4085 patients. On further analysis, only patients with intramuscular findings (IFs) incidentally detected on CT were included. Osseous or soft-tissue lesions with invasion into the musculature were excluded from the study. Patients with known or clinically suspicious muscle disorders were also excluded. Overall, 639 (15.64% of the 4085 analyzed cases) patients, 253 females and 386 males, with mean age 72.43 ± 12.02 years, were identified. Collected data were evaluated by means of descriptive statistics.

RESULTS

In the 639 patients, 917 IFs were identified. More often, several benign disorders were diagnosed (n = 803, 87.6%). There were hernias (33.5%), atrophy of different muscles (22%), lipomas (21%), intramuscular calcifications (8.7%), bursitis (1.2%) and intramuscular bleeding (1.1%). Malignant IFs (n = 114, 12.4%) included intramuscular metastases (11.9%) and lymphomas (0.6%). Most frequently, the identified IFs were localized in the abdominal wall musculature, paravertebral and gluteal muscles. In 657 cases (71.6% of all IFs), the identified muscle findings were not diagnosed by the radiologist who initially assessed the investigation.

CONCLUSION

CT can detect different incidental disorders within the skeletal musculature. Most of them were benign. However, malignant lesions can also occur. Therefore, skeletal muscles should be carefully evaluated on CT performed for other reasons. Advances in knowledge: IFs occur in 15.6% of CT investigations. Benign findings represent 87.6% and malignant lesions can be identified in 12.4%.

An Unusual Case of Extranodal Diffuse Large B-Cell Lymphoma Infiltrating Skeletal Muscle: A Case Report and Review of the Literature

Diffuse large B-cell lymphoma is extranodal in approximately 40% of cases, arising in nearly any organ system. DLBCL involvement of soft tissue and in particular skeletal muscle is extremely rare, comprising less than 1% of all extranodal non-Hodgkin lymphomas (NHL). We report a case of a 79-year-old man that presented with a DLBCL of the left triceps. In particular, we describe an unusual histologic appearance of pseudoglandular structures, resembling adenocarcinoma. We performed a review of lymphoma cases involving skeletal muscle diagnosed at our institution over the past 15 years as well as thorough PubMed review of the literature. We discuss the features of lymphoma involving skeletal muscle as it pertains to clinical characteristics, histologic subtype, tumor localization, diagnostic studies, therapy, and outcome. Finally, we highlight the diagnostic difficulties that can present in these rare and often challenging cases.

Non-Hodgkin's Lymphoma of Multiple Skeletal Muscles Involvement Seen on FDG PET/CT Scans

As normal healthy skeletal muscle does not contain lymphoid tissue, extra nodal lymphoma involving multiple muscles is rare, as well. This study reports a case of non-Hodgkin's lymphoma (NHL) of multiple skeletal muscles involvement and a review of differential diagnosis of it.A 37-year-old female presented to our hospital after being diagnosed with NHL for 7 months. She had received six courses of cyclophosphamide hydroxydaunorubicin oncovin prednisolone etoposide (CHOPE) chemotherapy. Then she felt pain and noticed swelling on her left calf. The fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) image showed abnormal focal FDG uptake in hypo-pharynx, which was the primary NHL and also in multiple groups of muscles in whole body. As the patient has history NHL, lymphoma of multiple muscle involvement was suspected.Finally, an ultrasound-guided tissue biopsy was performed on the left calf and histological examination yielded lymphomatous cells infiltration in the left gastrocnemius.Through this report, we emphasize that a multidisciplinary team approach with clinician, radiologist, and pathologist is essential for proper diagnosis, staging, and management of such rare lesions.

Diffusion-weighted imaging of skeletal muscle lymphoma

OBJECTIVE

Muscle lymphoma (ML) is a relatively uncommon condition. On magnetic resonance imaging (MRI), ML can manifest with a broad spectrum of radiological features. The aim of this study was to demonstrate the features of DW images of muscle lymphoma (ML).

MATERIALS AND METHODS

In our database, ten patients (six women and four men) with ML were identified who were investigated by magnetic resonance imaging including acquisition of DW images. DW images were obtained using a multi-shot SE-EPI pulse sequence. Apparent diffusion constant (ADC) maps were also calculated. Furthermore, fusion images were generated manually from DW and HASTE or T2W images.

RESULTS

On T2W images, all recognized lesions were hyperintense in comparison to unaffected musculature and on T1W images they were homogeneously hypointense. All lesions demonstrated low signal intensity on ADC images. The calculated ADC values ranged from 0.60 to 0.90 mm(2)s(-1) (mean value 0.76 ± 0.10; median value 0.78). On fusion images, all lesions showed high signal intensity.

CONCLUSIONS

ML demonstrated low ADC values and high signal intensity on fusion images suggesting high cellularity of the lesions.

Malignant and benign lesions of the skeletal musculature

There are several tumors and tumorlike conditions with variable biological behavior that may involve the skeletal musculature. The aim of this work was to review different intramuscular lesions and to provide a classification of muscle lesions based on their radiological patterns as well as to provide as a pictorial essay the imaging characteristics of typical muscle lesions. Radiologically, intramuscular lesions can manifest as solid masses, liquid or semiliquid masses, fat-containing lesions, diffuse muscle enlargement, and muscle calcifications. Additionally, lesions with mixed patterns can also occur. It is noteworthy that different malignant or benign muscle lesions can manifest with identical radiological patterns.

Muscle metastases: comparison of features in different primary tumours

Background

Muscle metastases (MM) from solid tumours are rare. The aim of this study was to describe radiological features of MM, and to compare their patterns in different malignancies.

Methods

A retrospective search in the statistical database of our institution revealed 61 cases of MM. Additionally, a retrospective search in Pubmed database was performed. Together with our cases the present analysis comprises 461 patients (682 MM).

Results

MM derived from the following malignancies: lung cancer (25.1%), gastrointestinal tumours (21.0%), and urological tumours (13.2%). Other neoplasias with MM were rare. MM were localised most frequently in the thigh muscles, the extraocular musculature, and the gluteal and paravertebral muscles. The localisation of MM was different in several primary malignancies.

On computed tomography (CT), five different patterns of MM occurred: masses with homogeneous contrast enhancement (type I, 46.5%), abscess-like lesions (type II, 27.7%), diffuse infiltration with muscle swelling (type III, 18.1%), intramuscular calcifications (type IV, 6.5%), or MM presented as intramuscular bleeding (type V, 1.2%). MM from several primary tumours manifested with different CT patterns.

On MRI, most MM were hyperintense in comparison to unaffected musculature in T2 weighted images and hypo- to isointense on T1 weighted images with a heterogeneous enhancement. There were no differences in MRI features of MM in different primary tumours. On ultrasound, most MM were hypoechoic. On positron emission tomography, MM presented as focally abnormal intramuscular uptake.

Conclusion

MM present with a broad spectrum of radiological features. Different CT imaging findings of MM were observed in different primary tumours. The localisation of MM also varies with different primary malignancies.

An unusual Hodgkin's lymphoma case presenting with upper extremity multiple masses

Almost always, Hodgkin's lymphoma presents with lymph node involvement. Primary extranodal lymphoma is rare and mostly has a type of non-Hodgkin's lymphoma. We present an unusual presentation of a Hodgkin's lymphoma in a 33-year-old man. There were numerous soft tissue masses localized in the subcutaneous tissue of the left arm along the neurovascular bundle and the ipsilateral axillary region. We found only one Hodgkin's lymphoma case that presented as an upper extremity mass reported in the literature. In cases where a great number of successively lined up soft tissue masses are detected on the extremity, lymphoma takes place among the differential diagnoses.

Magnetic resonance imaging of intramuscular metastases

OBJECTIVE

The aim of the present study was to analyse magnetic resonance findings of intramuscular metastases (IM) in a relatively large series.

MATERIALS AND METHODS

From January 2000 to January 2010, 28 patients (207 metastases) were retrospectively identified in the radiological database of the Martin-Luther-University. Several different scanning protocols were used depending on the localisation of IM. In 12 patients diffusion-weighted (DW) images were obtained with a multi-shot SE-EPI sequence. Apparent diffusion coefficient (ADC) maps were also calculated. Furthermore, fusion images were manually generated between the DW and half-Fourier acquisition single-shot turbo spin echo (HASTE) images.

RESULTS

On T2-weighted images, 97% of the recognised IM were hyperintense in comparison to unaffected musculature, and 3% were mixed iso- to hyperintense. On T1-weighted images most IM (91%) were homogeneously isointense in comparison to muscle tissue, whereas 4% were hypointense, and 5% lightly hyperintense. ADC maps were calculated for 91 metastases ranging from 0.99 to 4.00 mm(2)s(-1) (mean value 1.99 ± 0.66). ADC values of low (<1.5) signal intensity (SI) were identified in 26%, moderate SI (from 1.5 to 3.0) in 68%, and high SI (>3.0) in 6%. Of the IM that were investigated with contrast medium, 88.5% showed marked enhancement. It was homogeneous in 88% and heterogenous in 6%. Rim enhancement with central low attenuation was seen in 6%. There was no difference in enhancement characteristics with respect to ADC values or fusion patterns. Peritumoral enhancement was identified in 2.4%.

CONCLUSION

Magnetic resonance features of muscle metastases are relatively typical and consist of round or oval intramuscular masses with well-defined margins, marked enhancement, low or moderate ADC values, and moderate to high signal intensity on fusion images.

MRI features of skeletal muscle lymphoma

OBJECTIVE

The purpose of this study was to assess the MRI findings of skeletal muscle lymphoma.

MATERIALS AND METHODS

MR images of pathologically proven lymphoma of skeletal muscle in 20 patients were retrospectively reviewed for the presence or absence of individual imaging findings. Nine patients had primary muscle lymphoma, and 11 patients had muscle metastasis from systemic lymphoma.

RESULTS

The initial manifestation of skeletal muscle lymphoma was a muscle mass in 15 patients (75%) and abnormal muscle signal intensity in five patients (25%). Muscle enlargement was found in all cases. Long segmental involvement with orientation of the tumor along muscle fascicles was found in 15 patients (75%). Seventeen patients (85%) had traversing vessels within involved muscles. All of the tumors had equal to slightly increased signal intensity compared with normal muscle on T1-weighted images and intermediate signal intensity compared with fat on T2-weighted images. Among the 19 patients who underwent contrast-enhanced imaging, skeletal muscle lymphoma exhibited diffuse homogeneous enhancement in 13 patients (68%), predominantly peripheral thick bandlike enhancement in four patients (21%), and marginal septal enhancement in two patients (11%). Thick irregular enhancement of both deep and superficial fascia was found in 16 patients (84%), and one patient (5%) had deep enhancement only. Subcutaneous stranding was found in 16 patients (80%) and skin thickening in four patients (20%).

CONCLUSION

Skeletal muscle lymphoma has distinctive MRI features that help differentiate it from other soft-tissue tumors and tumorlike lesions.

Clinicopathologic features of primary lymphoma in soft tissue

By reviewing 3725 lymphomas diagnosed in our institution from 1999 to 2010, we found eight cases (0.21%) of primary lymphoma in soft tissue with comprehensive histologic and immunohistochemical studies. Of the eight cases of primary lymphoma in soft tissue, two patients were male and six were female. The mean age was 54.8 years with range from 23 to 76 years. The greatest diameter of tumor ranged from 1.3 to 20 cm with an average diameter of 7.5 cm. Six cases were diffuse large B-cell lymphoma (DLBCL), subclassified as three DLBCL non-germinal center B-cell phenotype, one DLBCL germinal center B-cell phenotype, and two (Epstein-Barr Virus) EBV-positive DLBCL of the elderly; one case was anaplastic large cell lymphoma, ALK-positive; and one case was peripheral T cell lymphoma, not otherwise specified. Follow-up was available for four patients. One patient who refused further therapy died of the disease at 2 months after diagnosis. The other three patients with follow-up were alive without recurrence and metastatic disease at 9, 36, and 48 months, respectively, after excisional biopsy combined with appropriate chemotherapy and/or radiation therapy.

Skeletal muscle metastases: primary tumours, prevalence, and radiological features

BACKGROUND

Although skeletal muscles comprise nearly 50% of the total human body mass and are well vascularised, metastases in the musculature are rare. The reported prevalence of skeletal muscle metastases from post-mortem studies of patients with cancer is inconstant and ranges from 0.03 to 17.5%.

MATERIALS AND METHODS

Of 5,170 patients with metastasised cancer examined and treated at our institution during the period from January 2000 to December 2007, 61 patients with muscle metastases (80 lesions) were identified on computed tomography (CT). Genital tumours (24.6%) were the most frequent malignancies metastasising into the skeletal musculature, followed by gastrointestinal tumours (21.3%), urological tumours (16.4%), and malignant melanoma (13.1%). Other primary malignancies were rarer, including bronchial carcinoma (8.2%), thyroid gland carcinoma (4.9%), and breast carcinoma (3.3%). In 8.2%, carcinoma of unknown primary was diagnosed.

RESULTS

Skeletal muscle metastases (SMM) were located in the iliopsoas muscle (27.5%), paravertebral muscles (25%), gluteal muscles (16.3%), lower extremity muscles (12.5%), abdominal wall muscles (10%), thoracic wall muscles (5%), and upper extremity muscles (3.8%). Most (76.3%) of the 80 SMM were diagnosed incidentally during routine staging CT examinations, while 23.7% were symptomatic.

CONCLUSION

Radiologically, SMM presented with five different types of lesions: focal intramuscular masses (type I, 52.5% of SMM), abscess-like intramuscular lesions (type II, 32.5%), diffuse metastatic muscle infiltration (type III, 8.8%), multifocal intramuscular calcification (type IV, 3.7%) and intramuscular bleeding (type V, 2.5%).

Lymphoma presenting as a musculoskeletal soft tissue mass: MRI findings in 24 cases

The purpose was to describe the MRI morphological features and signal intensity (SI) characteristics of 24 histologically proven cases of musculoskeletal soft tissue lymphoma presenting clinically as a suspected primary soft tissue sarcoma. This was a retrospective review of clinical notes and MRI studies of 24 patients with a histologically confirmed diagnosis of lymphoma. All patients presented to a specialist orthopaedic oncology unit with a suspected primary soft tissue sarcoma. Features assessed included lesion size and morphology, location, extension across anatomical compartments and signal intensity characteristics. The lesions were predominantly poorly defined with peritumoral oedema in ten cases. All tumours were of intermediate T1W SI, while 85% of lesions also showed intermediate T2W SI. Almost all cases that were located just deep to the fascia showed subcutaneous extension, while 50% had involvement of more than one muscle compartment. In 29% of cases, there was extension of tumour along the neurovascular bundle. Histo-pathologically, 23 lesions were non-Hodgkin's B-cell lymphoma. The MRI features of primary musculoskeletal soft tissue lymphoma include a mass with intermediate SI on T1W and T2W images, involvement of more than one anatomical compartment, subcutaneous extension and extension along the neurovascular bundle.

Hodgkin and non-Hodgkin lymphoma of the head and neck: clinical, pathologic, and imaging evaluation

Lymphomas are subdivided into HL and NHL and are more specifically classified into subtypes of HL or NHL according to the WHO classification. HLs involve the lymph nodes predominantly and only approximately 5% arise in extranodal sites, whereas 30% of NHLs present in extranodal sites. Imaging studies, including CT and MR imaging, cannot distinguish [figure: see text] HL from NHL, and cannot differentiate their various subtypes, necessitating a pathologic diagnosis. Clinical parameters, however, can be helpful in differentiating the two broad categories of lymphomas, and subtypes of lymphomas have predilections for different sites within the head and neck. HL is most commonly located in the lymph nodes of the neck and mediastinum. Marginal-zone lymphoma has an affinity for the ocular adnexa, salivary glands, larynx, and the thyroid gland. Diffuse large B-cell lymphoma is commonly encountered in the paranasal sinuses, mandible, maxilla, and Waldeyer ring. Burkitt lymphoma occurs more frequently in children and young adults and frequently affects the maxilla and mandible, with a greater distribution of involvement at a lower frequency. On imaging studies, the lymph nodes of HL and NHL are homogeneous and variable in size, with an average diameter from 2 to 10 cm. They may enhance slightly to moderately, display necrosis before and after treatment, and display calcification post-treatment. NHL in extranodal sites in the head and neck (nasopharynx, Waldeyer ring, oral cavity, and larynx) manifests frequently as a submucosal mass accompanied [figure: see text] by polypoid, bulky masses with a smooth mucosal surface. Clinically aggressive lymphomas, such as Burkitt lymphoma, diffuse large B-cell lymphoma, and NK-/T-cell lymphomas are characterized by destruction of the maxilla, mandible, and bones around the paranasal sinuses, which is indistinguishable from bony destruction in other malignant tumors, such as SCC. Contrast CT is indicated for evaluation of cervical lymph nodes; the chest, including the mediastinum; the pelvic cavity; paranasal sinuses; and orbits. CT is also useful for detection of bone destruction involving the base of the skull, paranasal sinuses, and the mandible or maxilla. MR imaging is preferred for the assessment of extension of lymphomas to different fascial spaces (parapharyngeal, masticator, infratemporal fossa, tongue, and nasopharynx) and for intracranial extension. Lymphomas are isodense to muscle on CT and circumscribed with distinct margins that occasionally display extranodal extension with less-well-defined margins and areas of necrosis within the tumor matrix. Lymphomas appear low in signal intensity on T1-weighted images and low to high in signal intensity on T2-weighted images, with variable, but usually low, enhancement following introduction of Gadolinium-DTPA (Gd-DTPA) contrast material.

Primary muscle lymphoma

Primary muscle lymphoma is rare. Less than 50 cases have been described. The clinical and radiological features of muscle lymphoma are presented in this series of six cases. Most patients present with solitary or multiple masses which may be painful. Clinical presentation varies from the indolent to the rapidly progressive. Systemic symptoms occur in a minority. In most cases, ultrasound shows an ill-defined hypoechoic mass but apparent coarsening of fibroadipose septa and swelling of muscle bundles may occur. CT shows an iso/hypo dense mass. On MR the mass appears iso/minimally hyperintense to muscle on T1W and enhances, and hyperintense on T2W, proton density and fat suppression sequences. Infiltration of the subcutaneous fat is a striking feature in a majority of cases on CT and MR. The diagnosis can be established by ultrasound guided biopsy and should be performed urgently in HIV positive patients to exclude pyomyositis.